Prospective Longitudinal Monocentric Study to Measure Limb Movement in Patients With FGFR3-related Skeletal Dysplasia (SKY-MOT3)

Prospective Longitudinal Monocentric Study to Measure Limb Movement in Patients With FGFR3-related Skeletal Dysplasia Using Syde®

The study aims to identify which Syde®-derived digital outcomes are reliable in FGFR3-related Skeletal Dysplasia. This requires to set-up a natural history study to measure limb movements in patients with ACH or HCH.

Study Overview

• Status: Recruiting
• Conditions: Achondroplasia; Hypochondroplasia

• Study Type: Observational
• Enrollment (Estimated): 40

Contacts and Locations

• Study Contact: Name: Ferial Toumi; Phone Number: +33 2 78 00 10 98; Email: ferial.toumi@sysnav.fr

Study Locations

• France
  • Paris, France, 75015
    • Recruiting
    • Hôpital Necker
    • Contact: Na An; Phone Number: +33 1 71 19 64 73; Email: na.an@aphp.fr
    • Principal Investigator: Genevieve Baujat
    • Sub-Investigator: Soo Kyung Kim

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Participants will be recruited from the patient registry of the Centre de Référence des Maladies Osseuses Constitutionnelles located at NeckerHospital / IMAGINE Institute. The APPT association (Association des Personnes de Petite Taille) will also help with the recruitment through flyers distribution. All visits will take place at Necker Hospital.

Description

Inclusion Criteria:

1. Aged 3 years old or older at the time of consent.

2. Written informed consent obtained:

   1. From the parent(s) or legal guardian(s) for participants under 18 years old.
   2. From participants 18 years old and older.
3. Affiliated to, or beneficiary of a social security category
4. Able to walk unassisted for at least 10 meters.
5. Genetically confirmed diagnosis with one pathogenic variant (ACMG class IV & V) of achondroplasia or hypochondroplasia.
6. Participant (and caregivers for participants under 18 years old) willing and able to comply with all study procedures including: questionnaires, Syde® related procedures

Exclusion Criteria:

1. Subjects who have short stature condition other than ACH/HCH.
2. Presence of cognitive disorders that limit their understanding of the data collection process (training of device use and 4-week recording periods every 6 months, device return at the end of the study), the implication of the study and consent.
3. Presence or history of any concurrent disease or condition that could interfere with study participation, impact pediatric growth, affect motor or balance or gait function (such as neurological, endocrine, infectious, allergic, osteoarthritis, or inflammatory), assessed by the investigator.
4. Females who are pregnant, or planning to become pregnant during the study duration.
5. Body Mass Index = 35 kg/m2.
6. Recent upper and/or lower limbs injury (trauma/fracture or surgery) in the 6 months preceding inclusion.
7. Prior limb lengthening surgery or planned or expected to have limb lengthening surgery while enrolled in the study.
8. Presence of guided growth hardware (such as 8-plates) or planned orthopedic surgeries during the study.
9. Vulnerable patient (guardianship, curatorship or safeguarding of justice), unable to provide informed consent or who is unable to express their consent.

Study Plan

How is the study designed?

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Reliability of digital endpoint derived from Syde® assessed by the Intra-Class Correlation (ICC) for each recording period timepoint.	reliability assessed by the ICC (Intra-Class Correlation)for each recording period timepoint (baseline, 6 months, 12 months)	12 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
number of participants reaching 180 hours of recording during the recording periods defined in the protocol	Number of patients reaching 180 hours of recordings during the recording periods defined in the protocol (supposed optimal threshold for Syde®-derived digital endpoint computation) at baseline, 6 months, 12 months	12 months
Correlation between digital endpoints derived from Syde® and 6-minutes walk test (6MWT)	Correlation at baseline and at different timepoints between Syde® derived digital endpoint and 6MWT	12 months
Correlation between digital endpoints derived from Syde® and growth parameters	Correlation at baseline and at different timepoints between Syde® derived digital endpoints and annualized growth velocity, height Z-score, body proportion ratios	12 months
Correlation between digital endpoints derived from Syde® and Patient-reported Outcomes (PROs)	Correlation at baseline and at different timepoints between Syde® derived digital endpoints and PROs	12 months
Longitudinal Change in digital endpoints derived from Syde®	Change from baseline in digital endpoints derived from Syde® at 6 and 12 months	12 months
Qualitative interview exploring limitations on mobility and impact on daily life	caregiver and/or participant qualitative interview exploring limitations on mobility daily life	baseline
French System Usability Score (F-SUS) score at 6 months of Syde® use	French System Usability Score (F-SUS) at 6 months. The System Usability Scale is a 10-item questionnaire . It is a simple tool to measure the usability of an interactive system and it is widely used. For each item, the user is asked to express their level of agreement or disagreement from 1 (strongly disagree) and 5 (strongly agree).	6 months
Syde® movement reconstruction accuracy compared to Optical Motion Capture measures.	Stride detection accuracy of Syde®, stride length and stride velocity accuracy of Syde® and upper limb measures, compared to Optical Motion Capture measures	Baseline

Collaborators and Investigators

• Sponsor: SYSNAV
• Investigators: Principal Investigator: Genevieve Baujat, Hôpital Necker

Study record dates

Study Major Dates

• Study Start (Actual): February 6, 2026
• Primary Completion (Estimated): February 1, 2028
• Study Completion (Estimated): February 1, 2028

Study Registration Dates

• First Submitted: January 28, 2026
• First Submitted That Met QC Criteria: January 28, 2026
• First Posted (Actual): February 5, 2026

Study Record Updates

• Last Update Posted (Actual): February 20, 2026
• Last Update Submitted That Met QC Criteria: February 18, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Bone Diseases; Musculoskeletal Diseases; Genetic Diseases, Inborn; Osteochondrodysplasias; Bone Diseases, Developmental; Dwarfism; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Achondroplasia; Hypochondroplasia
• Other Study ID Numbers: PR5030-108; 2025-A01608-41 (Other Identifier: ANSM)

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No